This application claims the priority of Germany patent document 198 12 238.1, filed Mar. 20, 1998, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a method for controlling the yaw behavior of a vehicle.
A method of the generic type is described, for example, in the article xe2x80x9cFDRxe2x80x94Die Fahrdynamikregelung von Bosch [FDRxe2x80x94Driving Dynamics Control by Bosch]xe2x80x9d in ATZ Automobiltechnische Zeitschrift 96 (1994) 11, p. 674 et seq. According to this article, a setpoint for the yaw rate of a vehicle is determined in a driving dynamic controller from the vehicle speed and the steering angle, using a one-track model of the vehicle. In addition, an actual value for the yaw rate is determined by a sensor. The difference between the actual value and the setpoint for the yaw rate is determined and the controlling deviation is derived from that. From this, an intervention in the wheel brakes is derived, which stabilizes the vehicle.
It is also known from German patent document DE 42 26 746 C1 to influence the driving behavior of a vehicle as a function of the yaw behavior by intervening in the steering.
The object of the methods according to the prior art is to improve the stability of the vehicle in critical driving situations by intervening in the steering or by a braking intervention. However, a simple intervention in the steering or the brake does not permit optimum utilization of the possible forces that can be transferred to the road, and therefore does not achieve an optimum stabilization of the vehicle in critical driving situations.
The object of the invention is therefore to make the vehicle as controllable as possible in critical driving situations and at the same time to extend as much as possible the range of critical driving situations that can be controlled.
These and other objects and advantages are achieved by the method according to the invention, which controls the yaw behavior of the vehicle by determining a setpoint for the yaw rate based on the steering angle specified by the driver, and determined vehicle speed. An actual value for the yaw rate is also determined, and a signal for controlling deviation is then derived from the difference between the actual value and the setpoint of the yaw rate. This controlling deviation is then supplied to two controllers operating independently of one another. In one controller (the steering controller), a setpoint is determined for the wheel steering angle of the steered wheels while in the other controller, the brake controller, a setpoint is determined for the change in braking pressure of the braked wheels. Taking this value into account, a specified braking pressure is then determined. The corresponding specified braking pressure is then developed by braking pressure adjusting members in the wheel brake cylinders and the corresponding wheel steering angle is produced by steering adjusting members at the steered wheels.
Therefore, one advantage of the invention is that redundancy is created by diversity as a result of the independence of the two controllers. In the event of failure of one of the two controllers, the other is always available for controlling the yaw behavior of the vehicle. No error recognition is required and the errors that develop are compensated automatically to the extent physically possible. In particular, xe2x80x9csteeringxe2x80x9d is still possible using the brake if the steering controller fails.
Another advantage of the invention consists in the fact that the steerability of the vehicle is expanded to a wider range of vehicle states. It is equally advantageous that the controlling quality of the steering behavior is improved by the invention. The adaptation of the actual behavior to the specified behavior of the vehicle takes place more rapidly and with fewer controlling deviations.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.